Simple Spray Process Research Articles

A photothermal superhydrophobic coating with un-fluorinated modified CNTs for anti-icing applications on concrete

The problem of easy icing and difficult anti-icing on concrete pavement has prompted using superhydrophobic coatings as a potential solution. However, the coatings are prone to wetting failure after repeated icing-deicing cycles. In this study, a superhydrophobic and photothermal coating consisting of unfluorinated modified-carbon nanotubes (M-CNTs) and commercial epoxy is constructed by a simple spray process on concrete for anti-icing. Incorporating M-CNTs imparts the coating with exceptional superhydrophobic and photothermal characteristics, endowing the coating surface with excellent deicing under sunlight irradiation. The contact angle of the coating reaches 151° at −10 °C, and the freezing time extends from 55 s to 680 s. Under one sunlight intensity, the coating temperature rapidly increases from −10 ℃ to 81 ℃, and the ice changes from solid to liquid. It effectively acts as a barrier between water and the concrete surface, making it highly suitable and valuable in practical applications.

MXene-Decorated Smart Textiles with the Desired Mid-Infrared Emissivity for Passive Personal Thermal Management.

Multifunctional and long-term stable wearable heating systems have attracted extensive attention from experts, yet smart textiles that only rely on harvesting the body's heat without additional energy still face huge challenges in practical applications. Herein, we rationally prepared the monolayer MXene Ti3C2Tx nanosheets via an in situ hydrofluoric acid generation method, which was further employed to construct a wearable heating system of MXene @ polyester polyurethane blend fabrics (MP textile) for the passive personal thermal management through a simple spraying process. Owing to the unique two-dimensional (2D) structure, the MP textile presents the desired mid-infrared emissivity, which could efficiently suppress the thermal radiation loss from the human body. Notably, the MP textile with an MXene concentration of 28 mg/mL exhibits a low mid-infrared emissivity of 19.53% at 7-14 μm. Significantly, these prepared MP textiles demonstrate an enhanced temperature of more than 6.83 °C compared with those of favorably traditional fabrics, involving the black polyester fabric, pristine polyester polyurethane blend fabric (PU/PET), and cotton, suggesting a charming indoor passive radiative heating performance. The temperature of real human skin covered by MP textile is 2.68 °C higher than that covered by cotton fabric. Impressively, these prepared MP textiles simultaneously possess attractive breathability, moisture permeability, mechanical strength, and washability, which provide new insight into human body temperature regulation and physical health.

Precise Localization and Simultaneous Bacterial Eradication of Biofilms Based on Nanocontainers with Successive Responsive Property toward pH and ATP.

The bacterial colonization of surfaces and subsequent biofilm formation are a great threat in medical therapy and clinical diagnosis. The complex internal structure and composition sets an enormous obstacle for the localization and removal of biofilms. In this study, we proposed a novel biofilm-targeted nanocontainer with successive responsive property toward pH and ATP for precise localization and simultaneous bacterial eradication, with an acidic and adenosine triphosphate (ATP)-rich microenvironment within biofilms, formed due to the accumulation of fatty acids and ATP in the three-dimensional enclosed structure, integrated as two successive indicators to improve the precision of biofilm identification and removal. The biofilm-targeted nanocontainer was composed of a ATP-responsive zeolitic imidazolate framework-90 (ZIF-90) core loaded with Rho 6G and doxorubicin hydrochloride (DOX) encapsulated in the pH-responsive amorphous calcium carbonate/poly(acrylic acid) (ACC/PAA) shell. In the presence of biofilms, the ACC/PAA shell and ZIF-90 core were successively degraded by the accumulated H+ and ATP within biofilms, resulting in the release of fluorescence indicators and antimicrobial agents. On the other hand, to meet the application requirements of different biofilm scenarios, the pH response ability of the nanocontainers could be adjusted by changing the metallic ions (Ni2+, Zn2+, and Cu2+) doped into the structure of the ACC/PAA shell. Owing to excellent water dispersion of the pH/ATP double-responsive ZIF-90@Zn-ACC/PAA nanocontainer, precise localization and simultaneous bacterial eradication was successfully realized via a simple spray process. The successive pH/ATP two-step unlocking processes endowed the nanocontainers high precision for localization and simultaneous eradication of biofilms, which made the proposed nanocontainers high promising in food safety and medical treatment.

Preparation of nano-ZnO@polytetrafluoroethylene superhydrophobic coating and its anti-biological adhesion properties

Multifunctional superhydrophobic surfaces that are resistant to biological adhesion have great application potential in marine science, biomedicine, and food engineering. In this study, a superhydrophobic surface was prepared by a simple spraying process with blended nano-ZnO and polytetrafluoroethylene (PTFE). The prepared surface was characterized by fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM), and the influence of the mass ratio of PTFE to nano-ZnO and the spraying distance on the morphology and wettability of the coating were investigated. In addition, the friction resistance of the coating and its antibacterial properties for Escherichia coli, Staphylococcus aureus, and Candida albicans were studied. Results showed that the optimal mass ratio of PTFE to nano-ZnO was 4:1 and that the optimal spraying method was spraying from near to far. SEM images indicated a compact surface structure of the surface with a thickness of about 100μm and the substrate was tightly bonded with the coating. The superhydrophobic properties of the coating surface were stable after friction testing. More importantly, the coating showed excellent antibacterial performance, which provides a reference for the research and application of superhydrophobic coatings with desirable anti-biological adhesion properties.

Anti-icing and anti-frost properties of structured superhydrophobic coatings based on aluminum honeycombs

Superhydrophobic coatings have many potential applications in prevention of ice, frost, condensation, and corrosion due to their strong hydrophobicity and self-cleaning function. However, superhydrophobic coatings do not have ideal mechanical stability in engineering applications, and the coatings lose their superhydrophobic properties with wear. We propose an innovative combination of a macroscopic aluminum honeycomb structure with a superhydrophobic coating to prepare a mechanically stable, structured coating by a simple spraying process. The coating showed excellent performance in laboratory ice, frosting, and outdoor ice tests. Compared with common superhydrophobic coatings, the total ice-up time of single droplet was prolonged by 190 s on a platform at −15 °C because of the reduced heat transfer between the macro-honeycomb wall and the droplets. After 300 wear tests, the frosting amount increased by only 0.03 g when the platform was tilted to 60% at −20 °C and 75 ± 5% humidity. In the outdoor ice test, no large area of ice was observed on the surface. Our findings provide a new strategy for industrialization of superhydrophobic coating, and our strategy has potential applications in anti-icing and anti-condensation for electrical equipment, drag reduction, and anti-corrosion.

Rich activated edges of hexagonal boron nitride flakes in-situ triggered by nickel nanoparticles to achieve efficient reduction of friction and wear

The application of hexagonal boron nitride (h-BN) nanosheets as lubrication additives has attracted tremendous attention due to their excellent stability and friction performance. However, the exfoliation and functionalization of h-BN nanosheets are difficult which appear to limit the practical application of them. Herein, we demonstrate that commercial h-BN flakes (h-BNFs) can be directly used to fabricate antifriction and antiwear coatings through a simple spraying process after mixing with nickel nanoparticles (Ni NPs). The experiment results and density functional theory calculations demonstrated that Ni NPs could in-situ promote nitrogen atoms to break down from the edges of h-BNFs, forming electron deficient h-BNFs and Ni NPs, and then the electron deficient Ni NPs would adsorb oxygen to generate superoxide radicals during friction process. The as-obtained superoxide radicals can react with the electron deficient h-BNFs, and these functionalized h-BNFs can stably adsorb poly-alpha-olefins (PAO6) molecules to form antifriction and antiwear tribo-films on the stainless steel (SS) substrates. Besides, the metal-edge interaction (SMEI) between Ni NPs and h-BNFs can accelerate PAO6 molecules converting into carbon based films on the counterpart. Fantastically, the antifriction and antiwear performance of SS have been greatly improved after coated by Ni/h-BNF composite coatings with PAO6, with friction coefficients (COFs) as low as 0.07 and wear rates less than 1.5 × 10−13 m3/(N·m), respectively. This finding opens up a new way for the practical application of commercial h-BNFs as low friction lubricants.

Durable and highly sensitive flexible sensors for wearable electronic devices with PDMS-MXene/TPU composite films

MXenes, as two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have very excellent electrical properties and surface activity and are increasingly used in supercapacitors, batteries, electromagnetic interference shielding, and composite materials. Still, the poor stability of MXene when exposed to aqueous oxygen and the poor ability to interact with the polymer matrix have become important factors limiting its’ practical applications. To enhance stability, highly conductive and stretchable Ti 3 C 2 MXene/TPU sensing elements were prepared by a simple spraying process using thermoplastic polyurethane (TPU) as a substrate, and the sensing elements were encapsulated by polydimethylsiloxane (PDMS) to obtain MXene-TPU/PDMS constructed flexible strain sensors with excellent performance. This strain sensor features low detection limits (less than 0.005%, 0.5 μm), a wide sensing range (0–90%), a short response time (120.1 ms), and excellent durability (>3000 cycles). This strain sensor can be applied to a range of applications such as health detection, motion signals, detection of robot movements, and wearable electronic devices.

A robust and repairable copper-based superhydrophobic microfiltration membrane for high-efficiency water-in-oil emulsion separation

The micro-/nanohierarchical super-wetting filter materials with low energy consumption, low-cost and high-efficiency have attracted tremendous attention. Moreover, traditional emulsion separation materials based on micro-/nanohierarchical structure are easy to be irreversibly damaged due to poor mechanical properties. In this work, a copper-based superhydrophobic microfiltration membrane was fabricated based on simple spraying process and short time self-assemble surface modification method. Only driven by gravity, the membranes maintained excellent water-in-oil emulsion separation performance with the efficiency higher than 99.975%, even after 10 separation cycles, the efficiency is still higher than 99.95%. After 50 sandpaper abrasion cycles, the membranes still displayed excellent separation efficiency through a simple re-modification process. The superhydrophobic microfiltration membranes also had the ability to resist acid and alkali. Robust and copper-based superhydrophobic microfiltration membranes with reversible repair property provide new ideas for the selection of stable emulsion separation materials, and have more advantages and potentials in practical applications.

High-Capacity Reusable Chitosan Absorbent with a Hydrogel-Coated/Aerogel-Core Structure and Superhydrophilicity under Oil for Water Removal from Oil.

In this work, inspired by the self-cleaning surfaces of fish scales, we prepared a porous chitosan aerogel (CSA) through a simple freeze-drying process. With the three-dimensional interconnected microstructure, the aerogel was highly porous (porosity > 98.16%) and ultralight with a density ranging from 10.19 to 36.05 mg/cm3. The core/shell structure of the CS-hydrogel-coated/CS-aerogel core (CSHA) was fabricated through a simple spray process. The aerogel with low-adhesion CS-hydrogel-coating exhibited superoleophobicity (θoil ∼ 162°) under water and superhydrophilicity (θwater ∼ 0°) in oil. The hydrogel coating as a switch of the absorbent resists the oil phase and induces permeation of the water phase into the aerogel easily and quickly. The dry aerogel core with a porous structure has become a huge storage space. Taking advantage of this structure, an absorption capacity of 147 times could be obtained for water. The unique water absorption process along with switching between the aerogel and hydrogel gives the CSHA incredible potential for oil purification applications on site. Using the CSHA for oil purification, the purity of the obtained oil can be as high as 99.8%. Importantly, two facile approaches, including redissolving and drying, were applied to recycle the aerogels. The natural hydrophilic aerogels are made from dissolution and regeneration of chitosan powder, which is green, low-cost, simple and easy to scale-up. Using the as-obtained high-capacity recyclable CSA for oil/water separation, the mixture can be separated with high efficiency, making it a favorable candidate for applications in large-scale separation of oil-water mixtures in the future.

A multifunctional polymer composite coating assisted with pore-forming agent: Preparation, superhydrophobicity and corrosion resistance

In this paper, a versatile low-cost and simple spraying process was reported for fabricating epoxy resin (EP)/fluorinated ethylene propylene (FEP)/modified ZnO (m-ZnO) superhydrophobic coating (EP/FEP/m-ZnO). The ZnO nanoparticles were modified by the low surface-energy material of stearic acid, and the pore-forming agent (NH4HCO3) was used to build micro/nano-structures. Results showed that the composite coating with 32 wt.% of m-ZnO, 5 wt.% of NH4HCO3 exhibits the optimum superhydrophobicity, with water contact angle (WCA) of 160° and sliding angle of 2°. More importantly, the WCA of the as-prepared composite coating still maintains more than 130° under strong acid or 3.5 wt.% NaCl aqueous solution for 270 h immersion, which demonstrates the excellent anti-corrosive performance of EP/FEP/m-ZnO superhydrophobic coating. The WCA of the EP/FEP/m-ZnO coating still kept 136° and only gained weight loss of 1.04% after being rubbed with 300 cycles, and the weight loss of EP/FEP coating is 18.85% under the same condition. All the above aspects are the direct evidences for the highest wear resistance of EP/FEP/m-ZnO superhydrophobic coating. Furthermore, the adhesive ability of the EP/FEP/m-ZnO composite coating was satisfied with the requirements of Grade 1, that standing for strong adhesion between the coating and substrate. Simultaneously, the soil and fly ash could be easily cleaned from the surface of superhydrophobic coating with flowing droplets, that showing unique self-cleaning property. Furthermore, the EP/FEP/m-ZnO superhydrophobic coating has excellent anti-corrosion performance. It is believed that the nano/micro structure formed by the inorganic filler m-ZnO and pore-forming agent of NH4HCO3 plays an important role. The suitable magnitude of pores has a positive meaning on fabricating the EP/FEP/m-ZnO superhydrophobic coating. The multifunctional coating has a high application value in condition of wear resistance, self-cleaning and anticorrosion, this facile and economic method may offer an effective strategy for surface and interface science and even industrial production.

Environmentally safe, durable and transparent superhydrophobic coating prepared by one-step spraying

High transparency, excellent durability and simple preparation process are the three main factors for practical application of superhydrophobic coatings. Herein, we prepared a superhydrophobic (SH) suspension composed of hydrophobic SiO2 nanoparticles (about 10 nm) and fluorine-free resin. The as-prepared (SH) suspension was used to fabricate an SH coating with high transparency and durability via a simple spraying process. We found that the microscopic surface topography, water contact angle (WCA) and transmittance of the coating strongly depends on the ratio of the resin to nanoparticles. The optimum coating had a static WCA of 160°, a SA less than 3° and a CAH less than 8°. The average transmissivity of the coated glass in the visible light range (400-800 nm) reached 91.03%. Meanwhile, the coating has high impalement resistant and excellent flexibility (bending radius of 3.0 mm). Simple spraying process and room temperature curable coating could be applied on various substrates and large-scale production. In addition, the coating can repel various mixed liquids and has good anti-fouling ability. These rapidly constructed coatings, without complicated modification and reaction may offer potential benefits for the fabrication of large-area, robust, superhydrophobic and self-cleaning surfaces.

A ZnO/porous GaN heterojunction and its application as a humidity sensor.

A heterojunction of ZnO/porous GaN (ZnO/PGAN) was fabricated and directly applied to a diode-type humidity sensor. ZnO disks were loaded onto PGAN using a spraying process. The structure and surface morphology of the ZnO/PGAN were characterized using X-ray diffraction and scanning electron microscopy. The heterojunction displayed an excellent diode nature, which was investigated using photoluminescence spectra and I–V characteristics. The excellent transport capability of ZnO/PGAN contributes to enhanced electron transfer, and hence results in high sensitivity and quick response/recovery properties under different relative humidity (RH) levels. In the range of 12–96% RH, a fast sensing response time as low as 7 s and a recovery time of 13 s can be achieved. The simple design of a ZnO/PGAN based humidity sensor highlights its potential in various applications.

Chemically Robust Superhydrophobic Poly(vinylidene fluoride) Films with Grafting Crosslinkable Fluorinated Silane

A superhydrophobic surface with excellent chemical stability was fabricated using the spraying method, one of the most efficient technologies for producing large-area coatings at low cost. Poly(vinylidene fluoride) (PVDF) was used as a hydrophobic polymer material, and heptadecafluoro-1,1,2,2,-tetra-hydrodecyl)trichlorosilane (FTS), which reacts with moisture during curing, was used to improve the water repellency and durability. Spray coating of PVDF alone yielded PVDF nanostructures described by the Cassie-Baxter model. The water contact angle of a water droplet on this surface, however, was 128°, indicating that the surface was not superhydrophobic. On the other hand, spray-coating a mixed PVDF-FTS solution provided a complex and homogeneous nanostructured surface with excellent water repellency and a contact angle of up to 159°. Immersion of the PVDF-only film for 20 min in N,N-dimethylformamide (DMF), a good solvent for PVDF, led to complete dissolution of the film. By contrast, the PVDF-FTS film maintained its superhydrophobicity with a water contact angle of 151° after 20 min of immersion in DMF, and still exhibited a high contact angle of 142° after 1 h. The PVDF-FTS film developed in the present work should enable the production of large-area superhydrophobic coatings at low cost using a simple spray process. Moreover, the PVDF-FTS film displayed excellent stability against solvents, thus increasing its suitability for robust superhydrophobic applications.

A robust superhydrophobic PPS-PTFE/SiO2 composite coating on AZ31 Mg alloy with excellent wear and corrosion resistance properties

Composite coatings consisting of polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE) and 40 nm silicon dioxide (SiO2) nanoparticles (PPS-PTFE/SiO2) with SiO2 in the range of 0–4 g/l were successfully prepared on AZ31 Mg alloys by a simple spray process. The morphology, composition, water contact angle (WCA), wear behavior and corrosion properties of the composite coatings were measured by using SEM, FT-IR, OCA20, sandpaper abrasion and electrochemical workstation, respectively. Effects of SiO2 content on the wear behavior and corrosion properties of the coatings were studied. It is found that micro-sized protrusions distribute on the surface of the coatings, and a fibrous-network structure of PTFE arranges on the protrusions. WCAs of the PPS-PTFE/SiO2 (0–4 g/l) coating are in the range of (152°–145.5°) ± 0.3° and the sliding angles (SAs) are less than 5°. The WCAs of the un-abraded and 10 m-abraded-on-sandpaper PPS-PTFE/SiO2 (4 g/l) coating are 145.5°±0.3° and 142.5°±0.3°, respectively, implying the PPS-PTFE/SiO2 coating is a robust superhydrophobic one with good wear resistance. Due to the superhydrophobic characteristics, the PPS-PTFE-based coatings show superior corrosion resistance in 3.5 wt% NaCl solution to pristine AZ31 Mg alloys. Owing to the excellent superhydrophobicity, wear resistance and corrosion resistance properties, the robust PPS-PTFE/SiO2 coating is regarded to possess great potential to be applied in automobiles and navigation industries in future.

ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature.

ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10–50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications.

Preparation and properties of biomimetic superhydrophobic composite coating

A nanosilica (SiO2)/polyurethane (PU) micro-nanocomposite coating with similar surface structure as a lotus leaf was prepared using a simple spraying process. The formation mechanism and structural characteristics of the coating were analysed. The coating surface was also characterised via scanning electron microscopy. The influence of the contents of SiO2, PU, and organosilicon on the coating surface structure and contact angle was studied. The results showed that the coating surface had a similar micro-nanostructure as the lotus leaf surface. When the content of organosilicon was greater than 15%, the water contact angle of the coating and sliding angle were 158 and 3°, respectively. This SiO2/PU micro-nanocomposite coating had superhydrophobic properties and repeated use performance.

A simple spraying process greatly enhanced field emission of novel T-ZnO-supported CNT emitters

T-ZnO-supported CNT emitters were fabricated by using a simple process involving two spraying steps followed by heat treatment in air.

An Organic Double-Layer Coating on Aluminum and Steel Substrates for Anti-Laser Protection

In this work, an organic double-layer protective coating (ODC) was fabricated through a simple spray process on aluminum and steel. The coating is built as double-layer structure of heat resist base layer and reflective surface layer. Laser with power 103~104Wcm-2was set to ablate samples for 4s, while the temperature of panels’ back were being measured. Also, reflectivity of the coating was tested. Results demonstrated that reflectivity of ODC was up to 94%, and the panels were less apt to be ablated by laser radiation after coated, while the temperatures measured were substantially lower compared to blank panels with respect to the coating structure and composition.

Preparation and application of biomimetic superhydrophobic silica and polyurethane composite coating

A nanosilica (SiO2)/polyurethane (PU) micro-nanocomposite coating with similar surface structure as a lotus leaf was prepared using a simple spraying process via a biomimetic method. In this process, SiO2 and organosilicon-modified PU were used as raw materials, and ethyl acetate was used as a dispersing agent. The formation mechanism and structural characteristics of the coating were analysed. The coating surface was also characterised via scanning electron microscopy. The influence of the contents of SiO2, PU, organosilicon on the coating surface structure and contact angle (CA) was studied and the coating was applied to the surface of different materials. The results showed that the coating surface had a similar micro-nanostructure as the lotus leaf surface. The mass ratio of SiO2 and PU was between 4:5 and 3:5. When the content of organosilicon was greater than 15%, the water CA of the coating and sliding angles were 158° and 3°, respectively. The prepared SiO2/PU micro-nanocomposite coating had superhydrophobic properties.

A multifunctional transparent superhydrophobic gel nanocoating with self-healing properties.

Inspired by mussels we designed a novel green superhydrophobic gel nanocoating with good transparency and stability through a facile copolymerization reaction at room temperature and a subsequent trimethyl silyl modified process, which is applicable to various substrates via a simple spray process without requiring toxic substances. Importantly, this well-designed nanocoating has rapid self-healing superhydrophobicity induced by usual organic solvents to face complicated work conditions, which satisfies the need of daily life and can be applied in industry as well.